Water-jet cutting devices are well known from the prior art. Water is placed under a high pressure of up to 7,000 bar by means of the pressure-generating unit and is conveyed through an outlet nozzle. In the outlet nozzle, the water accelerates to high speeds such that a water jet, with which the cuttable material is impinged upon for the purpose of cutting said material, is formed. Optionally, an abrasive material, such as for example fine garnet sand, is admixed with the water jet. It is known that water-jet cutting affords a number of technical advantages over other cutting methods, such as laser cutting or sawing, such as for example cutting without introduction of heat so that there is no risk of distortion in the cuttable material. Moreover, a particularly important advantage of water-jet cutting is that the water jet itself can make, in the cuttable material, its initial bore from which the cuttable material is cut. The making of this initial opening is also referred to as ‘piercing’ of the cuttable material.
Water-jet cutting can in principle be used for cutting nearly all common materials. A special feature arises, however, when cutting cuttable material made of glass, glass-fiber-reinforced plastic and carbon-fiber-reinforced plastic. In the case of such cuttable material, the piercing operation for making the initial opening is performed at a lower pressure in comparison with the subsequent cutting operation, since otherwise there is a danger of damaging the cuttable material, in particular of cracking or breaking the cuttable material in the region of the initial opening. For this reason, use is typically made of controllable pressure-generating units which are able to provide at least two different types of output pressures, a low pressure for piercing and a high pressure for cutting the cuttable material. The water pressure generated by the pressure-generating unit is typically subject to a pulsation, that is to say to a small temporal fluctuation. In order to produce as clean a cut as possible, this pulsation is normally damped using a pulsation damper or buffer volume firmly incorporated into the fluid line. However, said pulsation damper disadvantageously leads to a relatively long duration for the switching of the device between the low pressure for piercing and the high pressure for cutting.